The KGB (КГБ) is the common abbreviation for the Russian: Комитет государственной безопасности (Komitet gosudarstvennoy bezopasnosti or Committee for State Security). It was the national security agency of the Soviet Union from 1954 until 1991, and its premier internal security, intelligence, and secret police organization during that time. It's unusual because it is in the Archer universe, but at the same time, actually existed at one point.
Nikolai Jakov is a lieutenant general in the KGB. However, many of his subordinates call him Major, possibly as an in-joke. Rona Thorne was a sleeper agent for the KGB who was recently activated during the events of "Movie Star."
Like Odin, the KGB is shown to have the same office dysfunction as ISIS, such as Nikolai's relationship with Mallory, his assistant destroying the sample of Archer's DNA out of bitterness, numerous agents who pursued Sterling in Moscow one of whom beat his leader at saying arrest when they arrested the old lady with the fire extinguisher, having spies who work for other agencies in their midst without suspicion, etc.